1. Field of the Invention
This invention relates to a core drilling tool for bore-holes in rock.
2. Description of the Prior Art
German Pat. No. 29 53 873 discloses a tool wherein a universal joint is employed for connecting the core tube to the stator of a motor that operates on the Moineau principle and is driven by the drilling fluid. The core tube is installed in a manner such that it cannot be removed without first performing disassembly operations, so that once a core has been drilled out, it cannot be extracted until the tool has been hoisted to the drilling platform and the subsequent disassembly operations have been performed. In a tool of this type, the stator contains a central passage for the drilling fluid, bypassing the working chambers of the motor in order to supply fluid to the interior of the core tube before the drilling operation commences, the object being to flush the core tube clean, without starting the motor.
In addition to the above, U.S. Pat. No. 3,055,440 discloses a turbine-driven core drilling tool, from which a core tube insert can be hoisted to the drilling platform by means of a catcher device, via a central passage through the turbine, while the drilling tool otherwise remains in its installed state.
An object of the invention is to provide an improved core drilling tool which, when in the installed state, enables cores to be extracted by withdrawing the core tube as a separate compartment.